The nonstress test (NST) measures of the change in heart rate of the fetus in response to movement. It is a quick check to make sure the baby is in good health. During the NST, an elastic belt will be placed around the mother's stomach. It will hold a special sensor that will measure the fetus's heart rate. The test generally lasts for 20-30 minutes.
The doctor will want to get a heart measurement while your fetus is moving. When the fetus is moving around, the heart typically beats faster. If the fetus is asleep or resting, there may not be any movement for a short period of time. In this case, the doctor may try to wake the fetus by having you eat or drink something, or by using sound against the abdomen.
Your doctor may recommend this test during the third trimester, if you have a medical condition that could put you at risk for having problems with your pregnancy. Examples of conditions that could put you or the baby at risk include:
You may also have an NST if:
The NST is not always accurate. Sometimes the test suggests a problem even when the fetus is healthy (known as a false-positive result). If there is no change in fetal heart rate in response to fetal movement, your doctor may want to try another test to confirm the NST test results.
Your doctor may also suggest other tests to gather important information about the health of your fetus. A problematic test result, such as no increase in the baby's heart rate with movement, may suggest that you need special care. It does not necessarily mean that your fetus is in trouble. Your doctor will be able to answer questions and discuss any concerns you have about monitoring.
Family Doctor—American Academy of Family Physicians
The American Congress of Obstetricians and Gynecologists
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Women's Health Matters
Fetal nonstress test (NST). American Pregnancy Association website. Available at:
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Updated September 2, 2016. Accessed October 24, 2016.
Preboth M. ACOG guidelines on antepartum fetal surveillance. The American Congress of Obstetricians and Gynecologists. Am Fam Physician 2000;62(5):1184-1188.
Prenatal care and tests. Office on Women's Health website. Available at: https://www.womenshealth.gov/pregnancy/you-are-pregnant/prenatal-care-tests.html. Available September 27, 2010. Accessed October 24, 2016.
Routine prenatal care. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T114252/Routine-prenatal-care. Updated June 22, 2016. Accessed October 24, 2016.
Last reviewed October 24, 2016 by Michael Woods, MD
Last Updated: 10/24/2016